Canning



March 22, 1966 w. R. SCHACK ETAL 3,241,475

GANNING Original Filed Dec. 27, 1960 3 Sheets-Sheet 1 Inv enfors WARRENR. SHACK WAYNE E. LZVJNESTUN March 22, 1966 w. R. SCHACK ETAL 3,241,415

CANNING Original Filed Dec. 2'7, 1960 3 Sheets-Sheet z Inventors WARRENR. HI -JACK WAYNE E. L ZVINESTUN March 22, 1966 w. R. SCHACK ETAL 3,

CANNING Original Filed Dec. 27, 1960 3 Sheets-Sheet 5 Rig-5 InventorsWARREN H.5HAC'K WAYNE E, LIVJNEI'ETDN United States Patent 7 Claims.(Cl. 99-249 This application is a division of our copending parentapplication S.N. 78,628 filed December 27, 1960, now abandoned.

This invention relates to the sterilizing and canning of food products,and more particularly concerns an improvement in sterilizing and canningfoods at superatmospheric pressure. It is to be understood that bycanning we refer to packing of food in rigid sealed containers, usuallymetal or glass, under conditions which permit the packaged item to beindefinitely shelf-stable at normal room temperatures.

Generally, canned food products have exhibited characteristic unnaturalflavors to the consumer. With the advent of improved transportation anddistribution of fresh foods, and the widespread use of otherpreservation techniques, such as freezing, the unnatural flavors ofcanned products have become, by comparison, more noticeable to theconsuming public. In some instances this factor is thought to havecontributed to consumer rejection of otherwise wholesome and stablecanned items.

The unnatural flavors are encountered in both meat and vegetableproducts. Certain of the unnatural flavors result from the foodpreparation method and are identified as cooked in the can or boiledflavors. It is our belief that they are promoted by at least twoconditions heretofore encountered in canning operations, namely,overcooking, and cooking in a sealed container in the presence ofrelatively large portions of liquid diluting material which is normallycanned with the food product. These unnatural flavors are not to beconfused with a metallic taste sometimes imparted to food packed inmetal cans, the latter being a characteristic of the container ratherthan the food preparation.

In the usual canning process the cans are filled with product formula,including liquid constituents or fillers, sealed, and retorted in largebatches. Retorting, while primarily intended to sterilize the product,also cooks it within the sealed can. It cannot be said that all bacteriaand spoilage organisms are destroyed during retorting, but commerciallyacceptable and nutritionally safe sterilization levels may be obtainedby holding the product at elevated temperatures for periods of timeinversely proportionate to the temperature. That is, generally at highertemperatures shorter periods of time are lethal for a sufficientpercentage of bacteria to effect sterilization. Suitable time andtemperature requirements may be defined by F. values which are basicallytime equivalents at 250 F. Reference is directed to the National CannersAssociation Laboratory Manual for the Canning Industry, 2nd edition1956, for further information on this matter.

Temperatures must be held within practical limits to avoid excessivethermal damage to the product and to avoid excessive stresses upon thecans. Unfortunately, in the retorting process the time and temperatureconditions necessary to efiect sterilization also result inovertreatment of at least portions of the food product. In this regardit must be noted that heat transfer within the sealed can will result inthe outer portions or product reaching relatively high temperatures forlonger periods as contrasted with the central portions. Consequently,impairment of the organoleptic qualities occurs.

Additionally the heating of a product in the presence of large amountsof liquid, usually water, also appears to impair flavor or taste valuesof the product probably due to a loss of flavor material to the liquid.This eflect is similar to cooking in excess water or boiling oftenemployed by the homemaker with tough or poor quality foods. Furthermore,when food products are cooked in a closed container or vessel, anyundesirable volatile materials which would normally escape in homecooking will be retained within the product, probably in the dilutingagent.

The conventional retorting process, in addition to impairing certainfiavor values, is also time-consuming since it requires large batches ofcanned product to be placed in a retort vessel, which is then raised toa superatmospheric pressure and elevated temperature for a timesufficient for all of the product within each can to reach and hold agiven temperature until sterilized. Further, the cans must be cooled andthe pressure within the retort reduced before the latter may be openedand the cans removed.

In an attempt to overcome the disadvantage of retorting the canningindustry has directed much interest to processes for at least partiallysterilizing food product at high temperature and pressure before canfilling. One such process is taught in the Smith, Ball Patent No.2,541,113, the disclosure of which is included herein by reference. Thatprocess comprises heating of complete product formula to temperatures ashigh as 280 F., while under superatmospheric pressure, to effect partialsterilization; then filling into partially pre-sterilized cans at areduced but still superatmospheric pressure; and finally completing thesterilizing of both can and contents and subsequently cooling the canneditem.

While this process may largely overcome certain dis advantages ofretorting, such as time and labor requirements, it involves entirelydiiferent equipment requiring substantial capital expenditure. To date,it has not been widely accepted in the industry. Accordingly the presentinvention is an improvement over the process and systern disclosed inthe Smith, Ball Patent No. 2,541,113.

It is our stated belief that the unnatural flavors associated with priorart canning methods is due to heating the food product in the presenceof all the liquid requisite in the formula, and overcooking at leastportions of the material when adding sterilizing heat to the canneditem. Additionally in a process such as that of the Smith, Ball patent,damage may be inflicted by flashing the product through a widetemperature range of 20 F. or more directly from sterilizingtemperatures to much lower filling temperatures. The latter damageoccurs when the boiling point of the product drops below the actualproduct temperature (when pressures are instantaneously decreasedwithout first lowering temperatures substantially) resulting in internalexplosion of steam from beneath the surface of food material.

Therefore, it is a principal object of this invention to provide animproved system for continuously sterilizing and subsequently fillingfood product into containers at high temperature and superatmosphericpressures.

We have found that most objectionable unnatural flavors can be reducedby subjecting only a. portion of the food product formula, containingless than the requisite amount of liquid, to maximum temperatures, underpressure, for a time at least suflicient to substantially sterilize thatportion; and only then adding enough liquid to complete the formula at atemperature which will maintain the mixture at a sterilizing level.

We have also found that objectionable unnatural flavors can also bereduced by subjecting a complete food product formula to controlleddeaeration through rapid 3 pressure reduction limited to induce atemperature drop of up to about 20 F., and entirely at pressudes aboveatmospheric.

We have further found that objectionable unnatural flavors noteliminated heretofore by high pressure sterilizing processes may, to ahigh degree, be prevented by treating pumpable components of the productformula at temperatures and pressures in execess of can sealingconditions, while nonpumpables are treated separately at elevatedtemperatures and pressures substantially at the latter conditions. Suchtreatment of the pumpables is carried out as the material flows throughconduits carefully maintained at pressures which hold the boiling pointabove resident temperatures, gradually decreasing in the direction offlow to the can sealing conditions.

Accordingly our invention contemplates a pressure sterilizing andcanning process incorporating any of the foregoing steps wherein thefood product formula is first sterilized, and diluted prior to beinginjected into a can, and where such sterilized product containssufficient residual heat to also sterilize the interior surfaces of eachcontainer. In this regard we have found that the food material generallyrequires a greater level of sterilization (a higher F. value) forconfidence in acquiring nutritionally safe and shelf stablecharacteristics than required for a clean container. That is, the foodmaterial usually harbors greater numbers of bacteria and spoilageorganisms than the container surface, and consequently is preferablyheated to a higher temperature or held longer at sterilizingtemperatures, or both. Furthermore, it is usually required that the foodmaterial be at least partially cooked during the sterilizing operation;and at the high temperatures herein contemplated, sterilization takesplace far more rapidly than cooking. Accordingly the cumulative periodsfor food and container sterilization may be relied upon, and increasedwhere necessary, to accomplish the necessary degree of cooking.

The system for carrying out our process basically comprises a chambercapable of containing pressures above atmospheric wherein can fillingand sealing is effected, and a conduit extending therein for deliveringproduct formula from sterilizing apparatus. The sterilizing apparatusincludes a formula supply means, a pressurized means for addingsterilizing heat to formula received from the supply means, means foradding fluid to the formula after the sterilizing heat has been added,and a plurality of controllable pressure means connected serially withthe aforementioned elements and chamber.

A more complete understanding of our invention will be apparent from thefollowing description taken in conjunction with the drawings wherein:

FIGURE 1 is a diagrammatic view of the preferred sterilizing apparatusof the present system;

FIGURE 2 is a sectional plan view of a valve unit used in the system;

FIGURE 3 is a perspective view showing the interior of the pressurizedcan filling and sealing chamber of the present system; and

FIGURES 4 and 5 are diagrammatic views of modifications of the apparatusof FIGURE 1.

The preferred sterilizing system Preferably, all of the foregoingimprovements are incorporated in the present system, as illustrated inFIG- URE 1. Referring to that figure, the sterilizing system is seen tocomprise heating, dilution, and deaerating means serially connected bysanitary conduit to the interior of a pressurized can filling andsealing chamber generally 10 which is shown in detail in FIGURE 3.Formula components to be sterilized at high temperature and pressure aredelivered to a supply means, such as hopper 12, from which they arepumped into the system by a controllable pressure means, namely, feedpump 14.

The various pressure means are pumps (including pump 14) such asWaukasha impeller type pumps, located throughout the system, that arespeed controllable by means of variable speed transmissions to impartdesired pressures in the conduits. The desired pressures will bedependent upon the operating conditions, principally temperatures,employed for specific products. Generally the pumps are regulated todevelop pressures at or exceeding the vapor pressure of the liquidphase, usually water, of the formula at each zone of the system. Thiscan be accomplished by running an upstream pump at a slightly fasterrate than the next downstream pump, which then acts as a back pressurepump, or by introducing additional material between pumps.

From pump 14, material is forced through a conduit generally 16 to asecond feed pump 18. However, a return conduit 20 is connected to theconduit 16, through a return valve unit generally 22 near the dischargeside of pump 14, for diverting material to the hopper 12 when the systemis shut down. Also between pumps 14 and 18 another valve unit generally24 is provided to connect the conduit 16 with a source of hot wash waterthrough pipe 26, for flushing and cleaning the entire system at theclose of an operating run and/ or preparaory to a new run.

The preferred embodiment of our invention includes two means for addingheat to the material. In advance of the inlet side of the second feedpump 18, a steam line 28 is attached to the conduit 16 through a steamflow control valve 30 from a super-heated steam source, not shown. Steamintroduced to the system through flow control valve 30 is primarilyutilized for preheating the material to be sterilized by directinjection and admixture therewith. It also provides a portion of thedilution requirements of the formula. However, it will be appreciatedthat steam injection under certain conditions may provide the entiresterilization requirements and even all dilution water necessary to theformula.

A conduit 32 extends from the discharge side of pump 18 to a suitableheat exchanger generally '34, normally supplying sufiicient heat forsterilizing the food material. The material then passes into a holdingconduit 36 wherein sterilization is achieved. Any suitable heatexchanger operable at high pressure may be utilized in this system.However, we prefer to use a cylindrical scraped wall heat exchanger,such as a Votator. The Votator shown in FIGURE 1 comprises a steamjacketed vessel 44 having steam connections 46, 48 and an internalagitator or mutator, not shown, powered by an electric motor 50. Themutator is fitted with blades which continuously scrape the interiorsurface of the heat exchanger and maintain rapid transfer of heat to theproduct without burning.

In practice where a heat exchanger such as the Votator 34 is utilized,feed pump 18 preferably is regulated to impart a pressure on thematerial within the Votator about 15 p.s.i.g. above the steam pressuresupplied to the vessel 44 through connection 46. This precaution isadvisable not only to avoid the possibility of thermally damaging foodmaterial coming into direct contact with the interior surfaces of theheated vessel, but also to avoid flashing in the Votator which woulddisrupt pumping rates. Additionally, this margin of pressure is usuallysufficient to maintain the pressure on the food material passing throughholding conduit 36 above the liquid phase vapor pressure at thetemperatures encountered therein. The various temperature-pressurerelationships for steam and for products containing water as the liquidphase may readily be determined from standard steam tables, such asthose found in Perry, I. H., Chemical Engineer's Handbook 3rd Edition(1950) published by McGraw- Hill Book Co., Inc., included herein byreference.

With regard to the steam requirements for this system, any suitablesource of clean, dry steam sufiicient to supply the requisite rate,temperatures, and pressure may be employed. We have calculated that asystem for producing about 5,000,000 pounds of product annually wouldrequire a steam source capable of supplying about 110,000

pounds per hour at l602()0 p.s.i.g. The main steam supply would bereduced to appropriate pressures and rates at various locations in thesystem through valves, etc. Usual control valves operate at abouttwo-thirds capacity, i.e., the available pressure and rate on the highpressure side of a control valve should be about 50% more than the lowpressure requirements.

The holding conduit 36 must be of sufiicient dimensions to provide atransit time sufficient to effect sterilization of food material flowingtherethrough at about the temperature reached in the heat exchanger 34.Preferably the sterilization level should be sufficient for shelfstability of the product and the time will generally not exceed 4-5minutes. Conduit 36 may be insulated to preserve the temperature of thematerial leaving the heat exchanger 34; however, only a 25 F.temperature loss has been experienced when left uninsulated.

Holding conduit 36 extends to a back pressure pump 52 operable tomaintain, in cooperation with feed pump 18, a superatmospheric pressurein the system therebetween. However, preceding pump 52, means isprovided for adding fluid to the material, such as by injecting aconstant flow of dilution liquid through an injection nozzle 54connected to the holding conduit 36. In turn injection nozzle 54 issupplied through a flow regulator valve '56 from a pressurized liquidheater generally 58 which is connected to a source of liquid supply, notshown, by pipe 60. The heater 58 should be capable of supplying theformula dilution requirements under superheated conditions as high asabout 270 F. in liquid state. According to specific operating conditionsthe dilution liquid at its source may be sterile, or partially sterileso long as the temperature of the diluted material is sufficiently highin temperature to maintain sterilization during the remaining period ofthe canning process. A sanitary city water supply is normally the liquidsource.

Downstream from the back pressure pump 52, diluted formula is directedthrough one of two parallel alternate paths to a flash deaeratorgenerally 64. As illustrated in FIGURE 1, a back pressure valve 66 and abypass line 68 are connected in parallel between two valve unitsgenerally 70 and 72. Another valve unit generally 74 is connectedbetween valve 72 and a conduit 76 leading to the deaerator generally 64.Processed material normally flows from pump 52 through the bypass line68 into conduit 76 and deaerator 64; and valves 70 and 72 are positionedaccordingly. However, due to the high operating temperatures in thesystem, all of the pumping equipment is manufactured with hightemperature clearances and thus will not maintain pressures on wateralone, or on a thin, watery product formula. (Water is normally forcedthrough the system at commencement of operation while bringing theequipment to operating conditions.) Accordingly valves 70 and 72 areoperated to place the back pressure valve 66 (comprising a restrictedorifice) on stream for thin, watery materials. Furthermore where such aproduct is being processed, pump 52 may be allowed to idle, since theback pressure valve 66 will adequately maintain pressures upstream topump 18.

A divert conduit 78 is connected to the valve unit generally 74 forpurposes of selectively flushing the system upstream thereof, or fordumping product before it reaches the deaerator 64. Normally, however,valve 74 is positioned to direct flow from either bypass line 68 or backpressure valve 66 to the deaerator.

The deaerator 64 comprises a relatively large volume vessel 80 having aproduct discharge conduit 82, extending from the bottom thereof to adischarge pump 84, and a vapor exhaust line 86, extending from the topof the vessel through a pressure control valve 88. The pressure controlvalve 88 is automatically controlled, according to the system operatingconditions, to discharge steam and volatiles flashed from productentering the deaerator; and to limit the pressure differential withinthe vessel 80 to above atmospheric levels which induce a temperaturedrop of no more than about 20 F. in the product between conduits 76 and82. Temperature of the product exiting from the deaerator should beapproximately the can filling temperature, preferably between 250 F. and270 F. For this range the pressure within the deaerator generally 64should be from about '15 p.s.i.g. for the lower temperature to about 27p.s.i.g. for the higher filling temperature. Pressure control valve 88is adjusted accordingly. Discharge pump 84 functions to maintain apositive superatmospheric pressure level at the discharge of thedeaerator 64 and to propel the product formula through a deliveryconduit 90 into the pressure chamber generally 10.

Structure of the valve units generally 22, 24, 70, 72 and 74 is shown inFIGURE 2. Each valve comprises a conduit section generally 96 and anactuator section generally 98, the latter preferably being pneumaticallyoperated. However, other actuator apparatus, such as hydraulic orsolenoid devices, are suitable. The conduit section consists of a mainpassageway 100 closed by a cap 102 at one end and open at the other end.Two laterally extending passageways 104, 106 are spaced along the mainpassageway 100. Each passageway 100, 104, and 106 is adapted to bejoined to conduits in the described system. A plug 108 preferably blocksthe passageway 100 between lateral passageway 104 and the cap 102. Boththe plug 108 and cap 102 have central openings adapted to slidablyreceive a piston rod 110 extending from the actuator section 98 to apiston 112 within the main passageway 100. Suitable packing may beprovided at the plug 108 and cap 102 to prevent leakage from the highpressure system.

A pair of annular piston seats 114 and 116 located in the mainpassageway between passageway 104 and 106, and between passageway 106and the open end of passageway 100, respectively, cooperate with thepiston 112 to block off one opening of the passageways and direct flowthrough the other two. The actuator section 98 contains a piston 124attached to rod 110 which is biased toward one end of a cylinder 118 bya compression spring 120. A high pressure air line 122 is connected tothe latter end of cylinder 118 whereby, by controlling induction andexhaust of air to the cylinder, the piston 112 may be moved between thetwo positions. Preferably each such valve unit is positioned in thepiping system so that during normal operation conditions, flow isdirected between passageway 106 and the open end of passageway 100, ineither direction, so as not to be impeded by rod 110.

The pressurized filling chamber The chamber generally 10 illustrated inFIGURE 3, is preferably large enough to accommodate standard can fillingand sealing equipment and a crew of operating personnel to service theequipment and correct any malfunction thereof. Additionally the chamber10 houses auxiliary cooking apparatus to be utilized for components ofcanned product such as meat patties, steaks, etc., which cannot bepumped through the above-described system.

Specifically referring to FIGURE 3, it may be seen that the deliveryconduit 90 enters through one wall of the chamber 10 and extendsoverhead to a can-filling machine generally A valve unit 132 within thechamber 10 connects the delivery conduit 90 with a return conduit 134 tohopper 12 or some other suitable collecting vessel in case the fillingmachine 130 is shut down and the product must be diverted for re-use.Additionally, another valve unit 136, in delivery conduit 90, isconnected to a drainpipe 138 for dumping the system to a sewer. Thelatter is generally used when the system is being flushed following arun of product or just preceding a new run.

Also in FIGURE 3 may be seen a can delivery conveyor generally 140 and acan inlet valve generally 142 for passing empty cans from the outside tothe inside of the chamber 10. Inlet valve 142 is in the form of arotatable star wheel 144 positioned in an airlock generally 146 at oneend of the chamber whereby the cans may be delivered without loss ofpressure from the chamber 10. As illustrated, cans are received sidewiseinto the chamber and slide down guideway 148 which turns them 90 beforeentering a can cleaner generally 150. The latter apparatus merely rinsesthe cans, preferably with water at about 180 F. to remove dirt or otherforeign matter in conformance with federal government (USDA-MID)standards, but does not sterilize them, An air cleaner is alsocommercially available in lieu of a hot water can cleaner. The cans arethen delivered by an endless conveyor 15?. to the can filling machine130, wherein they are filled with the proper amount of hot sterilizedproduct from delivery conduit 90.

The endless conveyor 152 carries the cans adjacent to one end of a foodpreparation table generally 158 to the filling machine 130. The table158 extends toward another wall of the chamber wherein a product inletvalve generally 160, similar in construction to can inlet valve 142, islocated. Table 158 is employed for the preparation of non-pumpablecomponents of food products to be canned. As will be later made clear,these items, such as steaks, may be brought into the chamber throughinlet valve 160 and cooked in suitable apparatus such as hot fat cookersor infrared heating equipment, not shown, on the preparation table 158,from which suitable portions are placed Within each passing can onconveyor 152 by an operator or suitable automatic equipment.

After filling, the unsealed cans enter a lid-applying mechanismgenerally 166 from whence they pass into a standard closing machinegenerally 168. A supply of lids may be carried int-o the chamber 10through a personnel airlock shown generally at 170. Airlock 170comprises a small antechanrber 172 having an outer port 174 and an innerport 176, the latter leading into the chamber 10. Personnel and materialentering through the airlock 170 are held in the antechamber 172, withboth ports 174, 176 closed, while being relatively slowly brought up tothe pressure within chamber 10, the latter usually averagingapproximately 17 p.s.i.g.

Sealed cans, after passing through the closing machine 168, are runthrough a can washer generally 178, which is operated substantially atthe can temperature, to remove any spilled food material from theoutside thereof. The cans are thence discharged from the chamber throughan exit valve generally 180 substantially the same in construction asthe can inlet valve 142. Outside the chamber 10 and at atmosphericpressure the cans discharged from exit valve 180 proceed immediatelythrough a high temperature holding tunnel generally 182 which isregulated to maintain the exit temperature of can and contents for aperiod of time calculated to insure sterilization of the internalsurfaces of the cans. Dependent on the canning temperature, this perioddoes not usually exceed about ten minutes, and usually one to fiveminutes is sufiicient where the holding tunnel employs hot air at anambient temperature of 250 to 270 F. to maintain can temperature.Product leaving the holding tunnel 182 is immediately cooled in chamber184 by flushing with cold water. This is followed by the normal labelingand casing steps common to canning operations. However for other thansmall size cans it is advisable to locate the holding tunnel and somepartial cooling equipment within the pressurized chamber, for processingin accordance with the same time and temperature conditions, so thatdifferential pressures on interior and exterior large can surfaces willnot cause damage to the can.

Modified sterilizing systems FIGURES 4 and 5 illustrate modifiedembodiments of the sterilizing system of FIGURE l. Elements common toFIGURE 1 and to either FIGURE 4 or 5 bear the same reference characterswith prime and double prime exponents, respectively.

In FIGURE 4 a system omitting deaerating equipment is illustrated. Alsoa by-pass conduit 190, around the heat exchanger generally 34 andbetween conduits 32' and 36', is shown. The by-pass conduit 190 isconnected to conduits 32' and 36 by means of a pair of three-way valves192 and 194, respectively, so that an operator may elect to processmaterial without the heat exchanger under certain conditions.

Generally the heat exchanger 34 may be avoided where sufficient steammay be injected through control valve 3 to raise the material tosatisfactory sterilizing temperatures, without adding an excess of waterto the final product. (Under the same conditions the heat exchanger 34of the system in FIGURE 1 could also be bypassed.)

Furthermore the deaerating equipment may be omitted (as in FIGURE 4)where the system is to operate at sterilizing temperatures which canreadily be lowered to canning level solely by the addition of dilutionwater. In this instance the conduit 76' leads directly from backpressure pump 52 to the pressure chamber, generally 10'.

In FIGURE 5 another system is illustrated wherein steam injectionthrough control valve 30" is provided downstream of the heat exchangergenerally 34", in holding conduit 36", rather than upstream thereof.Also, in this embodiment a return conduit 196 to hopper 12" is connectedto the discharge end of the heat exchanger 34", at holding conduit 36",by a three-way valve 198. Following the point of addition of dilutionwater at nozzle 54", the modified embodiment may provide for deaerationequipment per FIGURE 1 or a direct connection to the pressure chamberequipment per FIGURE 4 under the same conditions imposed upon thoseembodiments.

The process The manipulative procedures of our invention will havebecome clear from the preceding description. However, the operatingdetails are dependent upon the sterilizing temperature selected whichmay range broadly from about 225 F. to about 400 F. in this system.Preferably, sterilizing temperatures between 250 and 300 F. areemployed. It has been stated that pressures throughout the various zonesof the system must be maintained above the vapor pressure of the liquidcomponents of the food product formula at the resident temperatures.This is to prevent boiling or flashing of the material uncontrollablyduring the process. Accordingly, pressures at the sterilizingtemperature, in the heat exchanger generally 34, should be in the rangeof 30 to 160 p.s.i.g.

In carrying out this method the more or less solid components of theproduct formula are prepared with substantially less water than thefinal product requires. These undiluted components must containsufficient liquid to be pumpable and usually constitute from 75% to ofthe final mixture. Preparation of these materials may be entail partialprecooking. They are introduced to the system through hopper 12 andpumped at from 10 to p.s.i.g. toward the heat exchanger.

Steam at above about 60 p.s.i.g. is injected into the undilutedcomponents in quantities sufficient to preheat the mixture to aboveabout 200 F. to 250 F. In some instances it is possible to provide theentire sterilizing heat requirements by injecting steam directly intothe undiluted components. However, as shown in FIGURE 1 we prefer topump the preheated material into a steamjacketed Votator wherein thetemperature is rapidly in erased to the sterilizing range of from 225 F.to 400 F., preferably 250 to 300 F. The undiluted material is heldsubstantially at this temperature, while flowing, for a period of timesufiicient to effect sterilization, which may be as much as about 240seconds but preferably 70 seconds or less. After a sufiicient period forsterilization of the unidluted material, dilution water is added at aconstant rate and at a temperature whereby the diluted material willstill be at a sterilizing temperature, preferably in the range of 250 to270 F., whereby the diluted material will be insured sterile. Thedilution water is preferably added in an amount slightly in excess ofthe requirements for the final formula, where deaeration of the mixtureis contemplated.

The diluted formula at this point may be placed directly in cans andsealed in accordance with our improved method. However, we prefer tofiash-deaerate the hot, diluted formula under superatmosphericconditions regulated to limit temperature drop during the deaerationprocess to no more than about 20 F. to a final temperature of about 250or more. The deaeration step is controlled to boil off or flash anyexcess dilution water and has been found to carry away volatiles whichevidently have heretofore contributed to a cooked-in-thecan flavor. Thediluted formula after deaeration is preferably maintained at 250 F. to270 F. and is placed in clean, unsterilized cans under superatmosphericpressure averaging p.s.i.g. or greater. The canning pressure ismaintained at a level which holds the boiling point of the formula aboveits filling temperature.

The filled cans are then sealed and delivered to atmospheric conditionswhere they are maintained in a heated environment at a temperature whichholds the interior of the can substantially at the filling temperaturewithout adding heat thereto. The sealed cans are maintained at closingtemperature for a period of time sufiicient to sterilize the innersurface of the container to an P. value of at least about FL This periodmay also be adjusted in accordance with the cooking requirements of theproduct and may be up to about 10 minutes but is preferably 5 minutes orless. Thereafter, the cans are cooled substantially to room temperatureand packed. However for other than small size cans it is preferable tomaintain the filled and sealed cans at elevated pressure throughout theperiod they are held at filling temperature and initially cooled. Alsofor larger cans a longer holding period will be preferred.

The following examples will serve to illustrate the present inventionbut are not to be considered in any way indicative of the limits of theinvention, reference being directed to the claims for that purpose:

Example I A corned beef hash formula was prepared, containing less waterthan required in the final product, and blended to a temperature of 150F. The formula comprised about 60.0% double ground beef trimmings, 12.0%dehydrated potatoes, 3.7% combined salt, sugar, and seasoning, and 24.3%water. This formula was pumped into a system similar to that shown inFIGURE 1, but omitting the heat exchanger, wherein injected steamsupplied all of the necessary heat. Formula at 150 F. was pumped at 60lb./min., 90 p.s.i.g., and steam at 332 F., 90 p.s.i.g. was injected atthe rate of 7.5 lb./min. The resultant mixture flowed through a holdingconduit at the rate of 67.5 lb./min. with a transit time of 46 secondsat 80-90 p.s.i.g. and 276-280" F. Dilution water at 106 F., 120 p.s.i.g.was added to the flow at a rate of 5 lbs./min.; and the resultantmixture at 262 F. was continuously moved from a back presture pump atthe rate of 72.5 lbs./min., 18-20 p.s.i.g. to a deaerator. The deaeratorvessel exhausted vapors at about 18-20 p.s.i.g. and 255 F. at the rateof approximately 0.5 1b./min.; and discharged product at 255 F., 18-20p.s.i.g. for delivery to the pressure chamber at the rate of 72 lbs/min.The completed formula at 255 F. was filled into cleaned, unsterilizedcans, sealed and held substantially at filling temperature for about 5minutes.

Example 11 75 lbs. per minute of an undiluted beef stew compositionconsisting of 23.1% cooked, cubed beef, 10.2% beef broth, 40% potatoes,13.3% carrots, 6% onions, 2% Water, and 5.4% combined flour, salt, beefsuet and flavoring, which had been blended to 170 F. was pumped to aVotator while injecting 5 lbs. of steam per minute before reaching theVotator. Temperature in the Votator was increased to 300 F., which washeld for two seconds, after which 20 lbs. per minute of water at F. wasadded to bring the beef stew to complete dilution at a temperature of270 F. The diluted mixture was deaerated, causing the temperature todrop to 255 F., at which temperature it was canned and sealed and heldat filling temperature for 5 minutes.

Example 111 75 lbs. per minute of undiluted beef stew components,prepared as related in Example II, was pumped to a heat exchanger adding5 lbs. of steam per minute prior to entry thereto. The undiluted mixturewas raised to a sterilization temperature of 270 and held at thattemperature while flowing through conduit for 70 seconds. Thereafter, 20lbs. per minute of water superheated to 270 F. was added to give atotally diluted formula at 270 F. The formula was deaerated as inExample I to 255 F. and injected into cans.

Example IV 75 lbs. per minute of the undiluted beef stew compositionprepared in accordance with Example II was pumped to a heat exchanger,adding 5 lbs. per minute of steam just prior to entering thereto. Themixture was raised to a sterilization temperature of 280 F. which washeld while flowing through a conduit for 20 seconds; after which 20 lbs.per minute of water superheated to 230 F. was added, giving a dilutedmixture at 270 F. The diluted formula was deaerated to a temperature of255 F., injected, and sealed in cans.

Example V A spaghetti and meat sauce mixture comprising:

Percent Blanched spaghetti r 36.9 Beef 17.2 Tomato paste 20.44 Cheddarcheese 4.0 Onions 4.0 Sugar 2.55 Salt 2.12 Water 12.0 Seasoning andvinegar .79

was prepared and heated to F. 70 lbs. per minute of the concentratedmixture was pumped through a conduit wherein 8 lbs. per minute of steam.was added to raise the temperature to about 270 E, which was held for 15seconds for sterilization. Approximately 22 lbs. per minute of water at210 F. was added to provide the dilution requirements. This material wasnot deaerated but dilution lowered the temperature to about 255 F. atwhich it was injected into cans under pressure, sealed and held inatmospheric air heated to 250 to 300 F. for a period of one minute tosterilize the cans. Can were subsequently chilled in tap water.

Our method also contemplates the addition of nonpumpable components ofproduct formula to the unsterilized cans under superatmosphericconditions wherein such items are heated to sterilizing temperatures inthe range of about 250 F. and placed in the cans apart from thesterilized pumpable components.

I 1 Example VI A concentrated spaghetti-meat sauce representingapproximately 75% of the final sauce formula, containing approximatelythe following ingredients:

Percent Ground beef 24.8

Onions 5.8 Tomato Paste 30.7 Cheddar cheese 5.8

Water 26.0

Sugar 3.68 Salt 3.07 Seasoning and vinegar .15

was prepared by heating to 170 F. The undiluted sauce was pumped to aheat exchanger at the rate of 75 lbs. per minute, adding 5 lbs. perminute of steam just prior thereto. The mixture was heated to 290 F. andheld for 5 seconds while flowing in a conduit. 20 lbs. per minute of 190diluting water was added to form a mixture at 270 F., which wascontinuously deaerated to a temperature of 260 F., and delivered forinjection into cans. Pre-blanched spaghetti was first heated to 250 F.in the can by direct steam injection. 4 ozs. spaghetti, 1 /2 ozs. steamas condensate, and 10 ozs. meat sauce were placed in each can, which wasthen sealed and held for l minute at 250 F.

Example VII To can beef steaks and gravy, a concentrated gravy formulawas prepared at 150 F., including the following ingredients:

Percent Water 62.5

Onions 19.5

Flour 10.5

Salt 3.0

Beef suet 3.0 Coloring and flavoring 1.5

This concentrated formula was pumped through a conduit at the rate of 30lbs. per minute, to which 5 lbs. per minute of steam was continuouslyinjected to provide all of the sterilization requirements raising thetemperature of the mixture to 295 F. at 55 p.s.i.g. Temperature andpressure were held for 5 seconds, after which 10 lbs. per minute ofdiluting water at 190 F. was added, giving a diluted formula at 270 F.The diluted gravy was deaerated to a temperature of 260 F. preparatoryto injecting into cans. Meanwhile, in the pressure chamber, inch thickboneless beef roundsteaks were heated under a bank of infrared lamps toa center temperature of about 220 F. preparatory to canning. Surfacetemperature of the steaks was approximately 225 F. In the pressurechamber 2 oz. of gravy at 260 F., and 4 oz. of the heated steaks wereplaced in each can which was subsequently sealed and held at atmosphericpressure for 10 minutes in air heated within the range of 250 to 300 F.The cans were subsequently cooled in tap water.

Example VIII Gravy was prepared in the identical manner as recited inExample VII for producing canned beefsteaks and gravy. The steaks,however, were prepared by taking 3- inch diameter molded and quickfrozen steaks at l F., averaging 2 oz. per steak, and heating in deepfat at 280 F. to an internal temperature of 220 F., 2 oz. of gravy at260 F. and 4 oz. of steaks were sealed in each can, which wassubsequently held for 5 minutes at its internal temperature by exposingto atmospheric pressure air heated to the range of 250 to 300 F. Thecans were cooled in tap water.

The method and system of this invention is also useful in preparing petfoods as follows:

Example IX An incompletely diluted dog food formula comprising about ofthe total formula and containing all of the solid constituents includingground meats, cereals, salt, iron oxide and sodium nitrite was blendedat approximately F. The undiluted formula was introduced into thepreviously described system of this invention and rapidly heated to 310F. under pressure, at which temperature it was held for 10 seconds. 5lbs. per minute of steam was injected into 80 lbs. per minute of theundiluted formula just prior to the heat exchanger. After the holdperiod of 10 seconds, 16 lbs. per minute of dilution water at 100 F. wasadded to bring the mixture to 101% of its requirements. Temperature ofthe diluted formula was then 270 F. This mixture was deaerated to 250 F.to flash off the excess water; and was injected into cans and sealed inthe pressure chamber. The canning temperature was held for 10 minutes toinsure sterilization of the internal wall of the container.

Example X The incompletely diluted dog food formula of the precedingexample was pumped at the rate of 80 lbs. per minute to a heatexchanger, adding 5 lbs. per minute of steam. Temperature of the mixturewas increased to 270 in the heat exchanger and held for a period of 240seconds. Superheated dilution Water at 270 F. was added at the rate of16 lbs. per minute to bring the mixture to 101% of its requirements. Thediluted mixture at 270 F. was deaerated to a temperature of 250 F. toflash off the excess liquid. Cans were filled in the pressurizedchamber; and held at the internal temperature under atmosphericconditions to insure sterilization of the container walls.

Example XI An incompletely diluted dog food formula was prepared inaccordance with Example IX and pumped at the rate of 80 lbs. per minuteto the heat exchanger, adding 5 lbs. per minute of steam. Temperature ofthe mixture was raised to 290 F. in the heat exchanger and held for aperiod of 35 seconds. Dilution water at 180 F. was added at the rate of16 lbs. per minute, resulting in a mixture at 270 F. and representing101% of the formula requirements. The diluted mixture was deaerated andcanned at 250 F. The cans were subsequently held at internal temperatureunder atmospheric conditions for a short period insuring sterilizationof the internal walls, and subsequently cooled.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. An improved system for sterilizing and subsequently canning foodproduct at high temperatures and superatmospheric pressures, said systemcomprising: supply means for maintaining a quantity of flowable foodmaterial formula; conduit means connected to said supply means; pumpingmeans to flow said formula under pressure from said supply means intosaid conduit means; heating means associated with said conduit means forincreasing the temperature of said formula to a sterilizing level justbelow the boiling point of said formula at the pressure within saidconduit means, said conduit means being of sufficient dimension tocontain said formula at about said sterilizing level for a periodsufficient to insure adequate sterilization thereof; liquid injectingmeans connected to said conduit means beyond said heating means to addliquid to said formula in an amount to complete at least the totalliquid requirement of the final product and to adjust the temperature ofthe flowing 0 material; a pressurized deaerator means in said conduitmeans downstream of said heating means to continuously remove volatilematerial from the heated flowing product and to controllably reduce thetemperature thereof; and filling means connected to receive heated anddiluted product from said conduit and place said product intocontainers, said filling means being enclosed in a chamber atsuperatmospheric pressure.

2. An improved system for sterilizing and subsequently canning foodproduct at high temperatures and superatmospheric pressures, said systemcomprising: supply means for maintaining a quantity of fiowable foodmaterial formula; conduit means connected to said supply means; pumpingmeans to flow said formula under pressure from said supply means intosaid conduit means; heating means associated with said conduit means forincreasing the temperature of said formula to a sterilizing level justbelow the boiling point of said formula at the pressure within saidconduit means, said conduit means being of suflicient dimension tocontain said formula at about said sterilizing level for a periodsufiicient to insure adequate sterilization thereof; pressurizeddeaerating means in said conduit downstream of said heating means tocontinuously remove volatile material from the heated flowing productand to controllably reduce the temperature thereof, and filling meansconnected to receive said product from said deaerating means and placesaid product into containers, said filling means being enclosed in achamber at superatmospheric pressure.

3. An improved system for sterilizing and subsequently canning foodproduct at high temperatures and superatmospheric pressures, said systemcomprising: a hopper for maintaining a supply of flowable food materialformula; a conduit transporting said formula from said hopper; a pumpconnected between said hopper and said conduit for forcing said formulaunder pressure through said conduit; a heating means in said conduitbeyond said pump to raise the temperature of said formula to asterilizing level; a section of conduit beyond said heating means, inthe direction of formula flow, said section being of sufficient lengthto provide a transit time for the flowing formula of sufficient durationfor said formula to attain a desired state of sterilization; a backpressure means in said conduit beyond said section for maintainingsutficient pressure on said formula in said heating means and saidsection to prevent boiling at the sterilizing temperature; a liquidnozzle fitting in said conduit beyond said section for adding liquid inan amount to complete at least the total liquid requirement of the finalproduct and to adjust the temperature of said formula; a pressurizedcontinuous flash deaerator connected in said conduit beyond said sectionand said back pressure means to continuously flash volatile materialfrom said product by slightly lowering the pressure thereon, saidlowered pressure being limited to cause a temperature drop of no morethan 20 F. in said product; and filling means connected to receiveheated and diluted product from said conduit and place said product intocontainers, said filling means being enclosed in a chamber atsuperatmospheric pressure.

4. An improved system for sterilizing and subsequently canning foodproduct at high temperatures and superatmospheric pressures, said systemcomprising: supply means for maintaining a quantity of fiowable foodmaterial formula; conduit means connected to said supply means; pumpingmeans to flow said formula under pressure from said supply means intosaid conduit means; heating means associated with said conduit means forincreasing the temperature of said formula to a sterilizing level justbelow the boiling point of said formula at the pressure within saidconduit means, said conduit means being of sufficient dimension tocontain said formula at about said sterilizing level for a periodsuflicient to insure adeq te s eri iz i n there f; iqu d i jecting meanscon nected to said conduit means to add liquid to said formula aftersaid period in an amount to complete at least the total liquidrequirement of the final product and to adjust the temperature of theflowing material; pres surized deaerating means in said conduit beyondsaid liquid injecting means, in the direction of formula flow, tocontinuously remove volatile material from the diluted product and tocontrollably reduce the temperature thereof; and filling means connectedto receive said product from said conduit means and place said productinto containers, said filling means being enclosed in a chamber atsuperatmospheric pressure.

5. The apparatus of claim 4 wherein pressure maintaining means arelocated at spaced locations in said conduit to controllably maintainselected superatmospheric pressures therein between said pumping meansand said filling means; said pressures generally decreasing beyond saidheating means in the direction of formula flow.

6. The apparatus of claim 5 including heated temperature holding meansconnected to said filling means to receive and maintain filled andsealed containers at substantially the filling temperature for a periodof time.

7. An improved system for sterilizing and subsequently canning foodproduct at high temperatures and superatmospheric pressures, said systemcomprising: a hopper for maintaining a supply of flowable food materialformula; a conduit for transporting said formula from said hopper; apump connected between said hopper and said conduit for forcing saidformula under pressure through said conduit; a heat exchanger in saidconduit beyond said pump to raise the temperature of said formula to asterilizing level; a section of conduit beyond said heat eX- changer, inthe direction of formula flow, said section being of suflicient lengthto provide a transit time for the flowing formula of suflicient durationfor said formula to attain a desired state of sterilization; a backpressure pump in said conduit beyond said section for maintainingsufiicient pressure on said formula in said heat exchanger and saidsection to prevent boiling at the sterilizing temperatures; a liquidnozzle fitting in said conduit beyond said section for adding liquid inan amount to complete at least the total liquid requirement of the finalproduct and to adjust the temperature of said formula; a pressurizedcontinuous flash deaerator connected in said conduit beyond said liquidnozzle fitting and said back pressure pump to continuously flashvolatile material from said product by slightly lowering the pressurethereon, said lowered pressure being limited to cause a temperature dropof no more than 20 F in said product; and filling means connected toreceive heated and diluted product from said conduit and place saidproduct into containers, said filling means being enclosed in a chamberat superatmospheric pressure.

References Cited by the Examiner UNITED STATES PATENTS 2,100,327 11/1937 Getchell 99249 2,182,335 12/1939 Davis 99-251 X 2,286,999 6/1942Smith 99-482 2,428,044 8/1947 Sharp et a1. 99273 XR 2,541,113 2/1951Smith et a1 99249' 2,857,081 10/1958 Lung 222255 2,862,821 12/1958Wilbur et a1. 99182 3,032,238 5/1962 Paulsen 222-255 OTHER REFERENCESUnit Operations of Chemical Engineering, Textbook, McCabe & Smith,published by McGraw-Hill Book Co., 1956, pages 102 and 103 relied on.

CHARLES A. WILLMUTH, Primary Examiner. ROBERT E. PULFREY, Examiner.

1. AN IMPROVED SYSTEM FOR STERILIZING AND SUBSEQUENTLY CANNING FOODPRODUCT AT HIGH TEMPERATURES AND SUPERATMOSPHERIC PRESSURE, SAID SYSTEMCOMPRISING: SUPPLY MEANS FOR MAINTAINING A QUANTITY OF FLOWABLE FOODMATERIAL FORMULA; CONDUIT MEANS CONNECTED TO SAID SUPPLY MEANS; PUMPINGMEANS TO FLOW SAID FORMULA UNDER PRESSURE FROM SAID SUPPLY MEANS INTOSAID CONDUIT MEANS FOR HEATING MEANS ASSOCIATED WITH SAID CONDUIT MEANSFOR INCREASING THE TEMPERATURE OF SAID FORMULA TO A STERILIZING LEVELJUST BELOW THE BOILING POINT OF SAID FORMULA AT THE PRESSURE WITHIN SAIDCONDUIT MEANS, SAID CONDUIT MEANS BEING OF SUFFICIENT DIMENSION TOCONTAIN SAID FORMULA AT ABOUT SAID STERILIZING LEVEL FOR A PERIODSUFFICIENT TO INSURE ADEQUATE STERILIZATION THEREOF; LIQUID INJECTINGMEANS CONNECTED TO SAID CONDUIT MEANS BEYOND SAID HEATING MEANS TO ADDLIQUID TO SAID FORMULA IN AN AMOUNT TO COMPLETE AT LEAST THE TOTALLIQUID REQUIREMENT OF THE FINAL PRODUCT AND TO ADJUST THE TEMPERATURE OFTHE FLOWING FOOD MATERIAL; A PRESSURIZED DEAERATOR MEANS IN SAID CONDUITMEANS DOWNSTREAM OF SAID HEATING MEANS TO CONTINUOUSLY REMOVE VOLATILEMATERIAL FROM THE HEATED FLOWING PRODUCT AND TO CONTROLLABLY REDUCE THETEMPERATURE THEREOF; AND FILLING MEANS CONNECTED TO RECEIVE HEATED ANDDILUTED PRODUCT FROM SAID CONDUIT AND PLACE SAID PRODUCT INTOCONTAINERS, SAID FILLING MEANS BEING ENCLOSED IN A CHAMBER ATSUPERATMOSPHERIC PRESSURE.